Silicon dioxide Janus nanosheets relative permeability modifier (RPM) for reducing subterranean formation water permeability in carbonate and sandstone formations

ABSTRACT

A silicon oxide Janus nanosheets relatively permeability modifier (RPM) for carbonate and sandstone formations. The silicon oxide Janus nanosheets RPM may be used to treat a water and hydrocarbon producing carbonate or sandstone formation to reduce water permeability in the formation and increase the production of hydrocarbons. The silicon oxide Janus nanosheets RPM for carbonate formations includes a first side having negatively charged functional groups and a second side having alkyl groups. The silicon oxide Janus nanosheets RPM for sandstone formations includes a first side having positively charged functional groups and a second side having alkyl groups. The negatively charged functional groups may include a negatively charged oxygen group groups and hydroxyl groups. The positively charged functional groups may include amino groups and an amine. Methods of reducing water permeability using the silicon oxide Janus nanosheets RPM and methods of manufacturing the silicon oxide Janus nanosheets RPM are also provided.

BACKGROUND Field of the Disclosure

The present disclosure generally relates to the production ofhydrocarbons such as oil and gas from subterranean formations. Morespecifically, embodiments of the disclosure relate to water control insubterranean wells for production of hydrocarbons.

Description of the Related Art

Water control presents a significant challenge in the production ofhydrocarbons, both financially and environmentally. For example, undersome estimations it requires at least the same amount of energy toproduce a barrel of water as it does to recover a barrel of oil. Excesswater production detrimentally affects the economic life of hydrocarbonproducing wells and also causes many other oilfield-related problems,such as scale deposition, fines migration, corrosion, etc.

SUMMARY

In the past decades, many different methods have been developed tocontrol water production in hydrocarbon wells. Such methods includingmechanical isolation and chemical treatments. A Relative PermeabilityModifier (RPM), among other chemical material systems, is considered asone method of controlling unwanted water production in hydrocarbonreservoirs. A RPM treatment is generally in the form of weak solution oflow viscosity and, can be pumped into a hydrocarbon formation, typicallyby bullhead injection or as fracture additives, to reduce waterpermeability without significantly affecting oil permeability.

A RPM treatment may be applied directly to producing wells and, in someinstances, to injection wells. The simplicity of deployment (forexample, bullhead injection requires no zonal isolation) and capabilityof disproportionate permeability reduction may render RPM anadvantageous water control method to cut production costs in thoseenvironments where zones cannot be mechanically isolated or permanenttotal blockage is not possible.

However, the majority of commercially available water control chemicals,including RPMs, are designed for sandstone formations and not suitablefor carbonate formations. The available water control chemicals are notdesigned to form chemical bonds to the carbonate rock surface underreservoir conditions. Moreover, commercially available water controlchemicals may not perform adequately in sandstone formations.Consequently, there is a need for an improved chemicals and techniquesfor controlling water production in and that may be used in bothcarbonate formations and sandstone formations.

In one embodiment, a silicon oxide Janus nanosheet relativelypermeability modifier (RPM) is provided. The silicon oxide Janusnanosheet RPM includes a functional group bonded to the first side, thefunctional group selected from the group consisting of COOH, COO⁻, OH,and O⁻, or the functional group selected from the group consisting ofNH₂ and an amine. The silicon oxide Janus nanosheet RPM also includes analkyl group linked to the second side, the alkyl group selected from thegroup consisting of a C8-C30 alkyl.

In some embodiments, the alkyl group is bonded to the second side by anoxygen atom. In some embodiments, the degree of hydrophobic alkylfunctionality of the second side is in the range of 0.01 weight (wt) %to 40 wt %. In some embodiments, the silicon oxide nanosheet has athickness in the range of in the range of 24 nanometers (nm) to 95 nm.

In another embodiment, a method for reducing water permeability of acarbonate formation is provided. The method includes introducing acarrier fluid that includes a silicon oxide Janus nanosheet relativelypermeability modifier (RPM) into the carbonate formation. The siliconoxide Janus nanosheet RPM includes a functional group bonded to thefirst side, the functional group selected from the group consisting ofCOOH, COO⁻, OH, and O⁻. The silicon oxide Janus nanosheet RPM alsoincludes an alkyl group linked to the second side, the alkyl groupselected from the group consisting of a C8-C30 alkyl.

In some embodiments, the alkyl group is bonded to the second side by anoxygen atom. In some embodiments, the degree of hydrophobic alkylfunctionality of the second side is in the range of 0.01 weight (wt) %to 40 wt %. In some embodiments, the silicon oxide nanosheet has athickness in the range of in the range of 24 nanometers (nm) to 95 nm.In some embodiments, the carrier fluid is a polar solvent. In someembodiments, the carrier fluid is water.

In another embodiment, a method of manufacturing a silicon oxide Janusnanosheet relatively permeability modifier (RPM) is provided. The methodincludes preparing a silicon oxide nanosphere and functionalizing thesurface of the silicon oxide nanosphere using an alkyl silane to producea surface-functionalized silicon oxide nanosphere. The method alsoincludes crushing the surface-functionalized silicon oxide nanosphere toform a silicon oxide Janus nanosheets RPM. The silicon oxide Janusnanosheets RPM includes a silicon oxide nanosheet having a first sideand a second side, a functional group bonded to the first side, thefunctional group selected from the group consisting of COOH, COO⁻, OH,or O⁻, and an alkyl group linked to the second side, the alkyl groupselected from the group consisting of a C8-C30 alkyl.

In some embodiments, the alkyl group is bonded to the second side by anoxygen atom. In some embodiments, the degree of hydrophobic alkylfunctionality of the second side is in the range of 0.01 weight (wt) %to 40 wt %. In some embodiments, the alkyl silane isoctyltrimethoxysilane (OTMS) or octadecyltrimethoxysilane (ODTMS). Insome embodiments, preparing a silicon oxide nanosphere includespreparing a template nanosphere of a polystyrene nanosphere, growingsilicon oxide on a nucleation site on a surface of the templatenanosphere, and removing the template nanosphere via heat.

In another embodiment, a method for reducing water permeability of asandstone formation is provided. The method includes introducing acarrier fluid that includes a silicon oxide Janus nanosheet relativelypermeability modifier (RPM) into the carbonate formation. The siliconoxide Janus nanosheet RPM includes a functional group bonded to thefirst side, the functional group selected from the group consisting ofNH₂ and an amine. The silicon oxide Janus nanosheet RPM also includes analkyl group linked to the second side, the alkyl group selected from thegroup consisting of a C8-C30 alkyl.

In some embodiments, the alkyl group is bonded to the second side by anoxygen atom. In some embodiments, the degree of hydrophobic alkylfunctionality of the second side is in the range of 0.01 weight (wt) %to 40 wt %. In some embodiments, the silicon oxide nanosheet has athickness in the range of in the range of 24 nanometers (nm) to 95 nm.In some embodiments, the carrier fluid is a polar solvent. In someembodiments, the carrier fluid is water.

In another embodiment, a method of manufacturing a silicon oxide Janusnanosheet relatively permeability modifier (RPM) is provided. The methodincludes preparing an oil-silane mixture that includes an alkyl silaneand adding a polystyrene-polyacrylic acid block copolymer to theoil-silane mixture to prepare an emulsion, the emulsion including adroplet having an external hydrophilic surface and an interioroleophilic surface. The method also includes dissolving an oil core ofthe droplet in a solvent to form a silicon oxide hollow nanosphere andcrushing the silicon oxide hollow nanosphere to form the silicon oxideJanus nanosheets RPM. The silicon oxide Janus nanosheet RPM includes asilicon oxide nanosheet having a first side and a second side, afunctional group bonded to the first side, the functional group selectedfrom the group consisting of NH₂ and an amine, and an alkyl group linkedto the second side, the alkyl group selected from the group consistingof a C8-C30 alkyl.

In some embodiments, the alkyl group is bonded to the second side by anoxygen atom. In some embodiments, the alkyl silane isoctyltrimethoxysilane (OTMS) or octadecyltrimethoxysilane (ODTMS). Insome embodiments, the oil-silane mixture is tetraethoxysilane (TEOS) andamido-propyltrimethoxysilane (APTMS). In some embodiments, the solventis hexane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the chemical structure of a silicon oxide Janus nanosheetrelatively permeability modifier (RPM) in accordance with an embodimentof the disclosure;

FIG. 2 is a block diagram of a process for using a silicon oxide Janusnanosheets RPM in accordance with an embodiment of the disclosure;

FIG. 3 is a schematic diagram depicting the mechanism of a silicon oxideJanus nanosheets RPM in a carbonate formation in accordance with anembodiment of the disclosure;

FIG. 4 is a schematic diagram depicting the mechanism of a silicon oxideJanus nanosheets RPM in a sandstone formation in accordance with anembodiment of the disclosure;

FIG. 5 is a block diagram of a process for the synthesis of a siliconoxide nanosheets RPM for a carbonate formation in accordance with anembodiment of the disclosure;

FIG. 6 depicts a chemical reaction scheme for producing a silicondioxide hollow nanosphere in accordance with an embodiment of thedisclosure;

FIG. 7 depicts a chemical reaction scheme for functionalizing theexterior surface of a silicon dioxide nanosphere in accordance with anembodiment of the disclosure;

FIG. 8 is a block diagram of a process for the synthesis of a siliconoxide nanosheets RPM for a sandstone formation in accordance with anembodiment of the disclosure; and

FIG. 9 depicts an example droplet having an oil core and a Janusinterface in accordance with an embodiment of the disclosure.

DETAILED DESCRIPTION

The present disclosure will be described more fully with reference tothe accompanying drawings, which illustrate embodiments of thedisclosure. This disclosure may, however, be embodied in many differentforms and should not be construed as limited to the illustratedembodiments. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art.

Embodiments of the disclosure include a silicon oxide (silica) Janusnanosheet relatively permeability modifier (RPM) for carbonateformations. The silicon oxide Janus nanosheets RPM may be used to treata water and hydrocarbon producing carbonate formation to reduce waterpermeability in the formation and increase the production ofhydrocarbons. The silicon oxide Janus nanosheets RPM includes ahydrophobic side having alkyl groups and an “anionic” side havingnegatively charged groups. As discussed in the disclosure, the alkylgroups may include C8 to C30 alkyls. The negatively charged groups mayinclude a negatively charged oxygen group groups and hydroxyl groups.

The silicon oxide Janus nanosheets RPM may be introduced into acarbonate formation such that the anionic side attaches to the rocksurface of pores of the carbonate formation via an ionic bond betweenthe negatively charged groups and the positively charged calcium ions(Ca²⁺) on the rock surface. The hydrophobic (opposite) side of thesilicon oxide Janus nanosheets RPM faces the pore space. When waterinvades the pore space, the hydrophobic alkyl groups collapse and from awater resistant barrier in the pore space that impedes or completelyblocks flow of the water. When oil invades the pore space, thehydrophobic alkyl groups extend and are soluble in the oil, enablingflow of the oil through the pore space.

The silicon oxide Janus nanosheets RPM may be synthesized from siliconoxide hollow nanospheres obtained commercially or prepared from templatespheres, such as polystyrene spheres. The hydrophobic side of thesilicon oxide Janus nanosheets RPM may be prepared by functionalizingthe exterior surface of the silicon oxide hollow nanospheres using analkyl silane, octyltrimethoxysilane (OTMS), octadecyltrimethoxysilane(ODTMS), or a combination thereof. The surface-functionalized siliconoxide hollow nanospheres may be crushed using a milling process toproduce the silicon oxide Janus nanosheets RPM for carbonate formations.In some embodiments, the silicon oxide nanosheets RPM has a thickness inthe range of in the range of 24 nanometers (nm) to 95 nm.

Embodiments of the disclosure also include a silicon oxide (silica)Janus nanosheet relatively permeability modifier (RPM) for sandstoneformations. The silicon oxide Janus nanosheets RPM may be used to treata water and hydrocarbon producing sandstone formation to reduce waterpermeability in the formation and increase the production ofhydrocarbons. The silicon oxide Janus nanosheets RPM for sandstoneformations includes a hydrophobic side having alkyl groups and a“cationic” side having positively charged groups. As discussed in thedisclosure, the alkyl groups may include C8 to C30 alkyls. Thepositively charged groups may include an amino (NH₂) group or amines(that is, molecules containing a basic nitrogen atom (N) with a lonepair of electrons).

The silicon oxide Janus nanosheets RPM may be introduced into asandstone formation such that the cationic side attaches to the rocksurface of pores in the sandstone formation via an ionic bond betweenthe positively charged groups of the cationic side and the negativelycharged silicate ions on the rock surface. The hydrophobic (opposite)side of the silicon oxide Janus nanosheets RPM faces the pore space.When water invades the pore space, the hydrophobic alkyl groups collapseand from a water resistant barrier in the pore space that impedes orcompletely blocks flow of the water. When oil invades the pore space,the hydrophobic alkyl groups extend and are soluble in the oil, enablingflow of the oil through the pore space.

In another embodiment, the silicon oxide Janus nanosheets RPM forsandstone formations includes a hydrophobic side having alkyl groups anda “covalent” side having hydroxyl groups or silane ester groups. In suchembodiments, the covalent side of the silicon oxide Janus nanosheets RPMmay attach to the sandstone rock surface via covalent bonding.

The silicon oxide Janus nanosheets RPM may be synthesized using anoil-silane mixture having an alkyl silane (for example,octadecyltrimethoxysilane (ODTMS)). The oil-silane mixture may includesilanes such as tetraethoxysilane (TEOS) andamido-propyltrimethoxysilane (APTMS). An emulsion may be formed havingspheres with a silicon oxide shell having an oil core and a Janusinterface that includes an external hydrophilic surface and an interioroleophilic surface. The internal oil core of the spheres may bedissolved using a solvent to form silicon oxide hollow nanosphereshaving an exterior surface with amino groups or amines and an interiorsurface with alkyl groups. The silicon oxide hollow nanospheres may becrushed using a milling process to produce the silicon oxide Janusnanosheets RPM for sandstone formations. In some embodiments, thesilicon oxide nanosheets RPM has a thickness in the range of in therange of 24 nanometers (nm) to 95 nm.

Structure of Silicon Oxide Janus Nano Sheets RPM for CarbonateFormations and Sandstone Formations

FIG. 1 shows the structure of a silicon oxide Janus nanosheet relativelypermeability modifier (RPM) 100 for carbonate or sandstone formations inaccordance with an embodiment of the disclosure. As discussed in thedisclosure, the silicon oxide Janus nanosheets RPM may reduce waterpermeability in subterranean carbonate or sandstone formations andimprove hydrocarbon production from such formations.

As shown in FIG. 1, the silicon oxide Janus nanosheets RPM 100 includesa silicon oxide nanosheet 102 having a first side 104 (referred to asthe “anionic” or “cationic” side) that includes negatively or positivelycharged functional groups and a second and opposite side 106 (referredto as the “hydrophobic” side) having hydrophobic functional groups. Asused in the disclosure, term “negatively charged groups” may includegroups that ionize by releasing a hydrogen (H) atom as a free proton. Asdiscussed infra, in some embodiments the first side 104 includesnegatively charged groups that enables the silicon oxide Janus nanosheet100 to attach to the rock surface of a carbonate formation viainteraction with calcium ions (Ca²⁺) present on the carbonate rocksurface. In other embodiments, the first side 104 includes positivelycharged groups that enables the silicon oxide Janus nanosheet 100 toattach to the rock surface of a sandstone formation via interaction withsilicate ions (for example, SiO₄ ²⁻) present on the sandstone rocksurface. The second side 106 having hydrophobic functional groupsprovides a hydrophobic surface to control oil and water flow.

As first shown in FIG. 1, the first side 104 includes groups Z bonded toa surface 108 of the silicon oxide nanosheet 102. In embodiments inwhich the silicon oxide Janus nanosheets RPM 100 is for use in carbonateformations, Z is selected from the group consisting of hydroxyl (OH) anegatively charged oxygen group (O⁻), and carboxyl (COOH, and COO⁻)—. Inembodiments in which the silicon oxide Janus nanosheets RPM 100 is foruse in sandstone formations, Z is selected from the group consisting ofNH₂ and an amine.

The second side 106 of the silicon oxide Janus nanosheets RPM 100includes groups G bonded to the opposite surface 110 of the siliconoxide nanosheet 102 and groups R bonded to groups G. G is an oxygen atom(O). R is selected from the group consisting of C8 to C30 alkyls (thatis an alkyl group having a number of carbon atoms in the range of 8 to30). The degree of hydrophobic alkyl chain functionality of the siliconoxide Janus nanosheets RPM 100 provided by the R groups may be in therange of 0.01 weight (wt) % to 40 wt %.

Process for Using Silicon Oxide Janus Nanosheets RPM in CarbonateFormations or Sandstone Formations

FIG. 2 depicts a process 200 for using the silicon oxide Janusnanosheets RPM in accordance with an embodiment of the disclosure.Initially, a silicon oxide Janus nanosheets RPM may be prepared (block202). The silicon oxide Janus nanosheets RPM may be prepared at awellsite or, in some embodiments, prepared offsite and then transportedto the wellsite. The silicon oxide Janus nanosheets RPM may be preparedbased on use in a carbonate formation or a sandstone formation. For acarbonate formation, as discussed in the disclosure, the silicon oxideJanus nanosheets RPM may have an anionic side having negatively chargedgroups and a hydrophobic side having alkyl groups. For a sandstoneformation, as discussed in the disclosure, the silicon oxide Janusnanosheets RPM may have a cationic side having positively charged groupsand a hydrophobic side having alkyl groups. In another embodiment, thesilicon oxide Janus nanosheets RPM for sandstone formations may have acovalent side having hydroxyl groups or silane ester groups and ahydrophobic side having alkyl groups.

Next, the silicon oxide Janus nanosheets may be mixed with a carrierfluid and introduced into one or more wells located in carbonateformations or sandstone formations (block 204). The carrier fluid may bea polar solvent (for example, water). In some embodiments, the siliconoxide Janus nanosheets may be introduced via bullhead injection. The oneor more wells may include producing wells, injection wells, or acombination thereof. After injection, the silicon oxide Janus nanosheetsRPM may attach to the rock surface in pores and other openings in thecarbonate formation or sandstone formation (block 206). In embodimentsused in carbonate formations, the silicon oxide Janus nanosheets RPM mayattach to the rock surface of a carbonate formation due to the ionicinteraction between the negatively charged side of the silicon oxideJanus nanosheets RPM and the positively charged calcium ions (Ca²⁺) onthe rock surface, such that the alkyl groups of the hydrophobic side ofthe silicon oxide Janus nanosheets are oriented toward a pore space orother opening. In embodiments used in sandstone formations, the siliconoxide Janus nanosheets RPM may attach to the rock surface of a sandstoneformation due to the ionic interaction between the positively chargedside of the silicon oxide Janus nanosheets and the negatively chargedsilicate ions on the rock surface, such that the alkyl groups of thehydrophobic side of the silicon oxide Janus nanosheets are orientedtoward a pore space or other opening.

Next, production operations may be initiated (block 208) to producehydrocarbons from a hydrocarbon-bearing carbonate formation or sandstoneformation with reduced water production from the one or more wellshaving the silicon oxide Janus nanosheets RPM. When water invadesopenings (such as pores) (block 210), the hydrophobic alkyl groupscollapse and from a water resistant barrier in the openings (such as inthe pore space) that impedes or completely blocks flow of the water(block 212). When oil invades the openings (block 214), the hydrophobicalkyl groups extend and are soluble in the oil, enabling flow of the oilthrough the openings (block 216).

FIG. 3 is depicts the mechanism of a silicon oxide Janus nanosheets RPM300 in a carbonate formation 302 in accordance with an embodiment of thedisclosure. FIG. 3 illustrates a pore 304 in the carbonate formation 302that enables the flow of hydrocarbons from a hydrocarbon reservoirlocated in the formation 302. As will be appreciated, such formationsmay also produce water. As described in the disclosure, the siliconoxide Janus nanosheets RPM 300 may modify the permeability of the pore304 to decrease the permeability of the pore 304 to water and withoutdecreasing the permeability of the pore 304 to hydrocarbons.

As shown in inset 306 in FIG. 3, the silicon oxide Janus nanosheets RPM300 includes a first side 308 having negatively charged groups (by wayof example, only a negatively charged oxygen group groups are shown inthe inset 306). The silicon oxide Janus nanosheets RPM 300 includes ahydrophobic side 310 opposite the first side 308 and having alky groups.As also shown in inset 306, the first side 308 interacts with thecalcium ions (Ca²⁺) on the surface 312 of the carbonate formation 302 toattach the first side 308 of the silicon oxide Janus nanosheets RPM 300to the carbonate formation. After attaching the second side siliconoxide Janus nanosheets RPM 300 to the carbonate formation, the secondside 308 of the silicon oxide Janus nanosheets RPM 300 is orientedtoward the pore space of the pore 304.

As illustrated in FIG. 3, the silicon oxide Janus nanosheets RPM 300provides different permeability of the carbonate formation 302 dependingon the fluid (that is, water or oil) in the channel 304. Line 314 isdirected to the mechanism of the silicon oxide Janus nanosheets RPM 300when water 316 is invading the pore 304, and line 318 of FIG. 3 isdirected to the mechanism of the silicon oxide Janus nanosheets RPM 300when oil 320 is invading the channel 304.

As shown in inset 322, when the water 316 is in the pore 304, thehydrophobic alkyl groups collapse and from a water resistant barrier 324in the pore space of the pore 304 that impedes or completely blocks flowof the water 316. In some instances, after collapse of the alkyl groups,a capillary effect may act to flow the water 316 in the oppositedirection of the water invasion, as shown by arrow 326.

As shown by line 318, when oil 320 is in the pore 304, the hydrophobicalkyl groups extend and are soluble in the oil 320, enabling flow of theoil 310 in the pore space of the pore 304.

FIG. 4 depicts the mechanism of a silicon oxide Janus nanosheets RPM 400in a sandstone formation 402 in accordance with an embodiment of thedisclosure. FIG. 4 illustrates a pore 404 in the sandstone formation 402that may provide for the flow of hydrocarbons from a hydrocarbonreservoir located in the formation 402 or the flow water. As describedin the disclosure, the silicon oxide Janus nanosheets RPM 400 may modifythe permeability of the pore 404 in the sandstone formation 402 todecrease the permeability of the pore 404 to water and withoutdecreasing the permeability of the pore 404 to hydrocarbons.

As shown in inset 406 in FIG. 4, the silicon oxide Janus nanosheets RPM400 includes a first side 408 having positively charged groups (by wayof example, amino (NH₂) groups are shown in the inset 406). The siliconoxide Janus nanosheets RPM 400 includes a hydrophobic side 410 oppositethe first side 408 and having alky groups. As also shown in inset 406,the first side 408 interacts with the silicate ions (SiO₄ ²⁻) on thesurface 412 of the sandstone formation 402 to attach the silicon oxideJanus nanosheets RPM 400 to the sandstone formation 402. After attachingto the sandstone formation 402, the second side 408 of the silicon oxideJanus nanosheets RPM 400 is oriented toward the pore space of the pore404.

As illustrated in FIG. 4, the silicon oxide Janus nanosheets RPM 400provides different permeability of the sandstone formation 402 dependingon the fluid (that is, water or oil) in the pore 404. Line 414 of FIG. 4is directed to the mechanism of the silicon oxide Janus nanosheets RPM400 when water 416 is invading the pore 404, and line 418 of FIG. 4 isdirected to the mechanism of the silicon oxide Janus nanosheets RPM 400when oil 420 is invading the pore 404.

As shown in inset 422, when the water 416 is in the pore 404, thehydrophobic alkyl groups collapse and from a water resistant barrier 424in the pore space of the pore 404 that impedes or completely blocks flowof the water 416. In some instances, after collapse of the alkyl groups,a capillary effect may act to flow the water 416 in the oppositedirection of the water invasion, as shown by arrow 426. As shown by line418, when oil 420 is in the pore 404, the hydrophobic alkyl groupsenable flow of the oil 410 in the pore space of the pore 404.

Synthesis of Silicon Oxide Janus Nano Sheets RPM for CarbonateFormations

FIG. 5 depicts a process 500 for the synthesis of a silicon oxidenanosheets RPM in accordance with an embodiment of the disclosure. Asdiscussed infra, silicon oxide nanosheets may be prepared from siliconoxide nanospheres. In some embodiments, silicon oxide hollow nanospheresmay be prepared using template nanospheres (block 502). In suchembodiments, template nanospheres (for example, polyvinylpyrrolidone(PVP)-stabilized polystyrene nanospheres) are prepared or obtained.Silicon oxide may be grown on the nucleation sites on the exteriorsurface by the template nanospheres, and the template nanospheres may beremoved after growth of a desired coating of silicon oxide. For example,polystyrene template nanospheres may be removed by burning off thepolystyrene core via heat treatment (such as heating to a temperature ofat least 500° C.).

FIG. 6 illustrates step 502 of the process 500 in accordance with anembodiment of the disclosure. As shown in FIG. 6, a template nanosphere600 (for example, a polyvinylpyrrolidone (PVP)-stabilized polystyrenenanosphere) is obtained. Silicon oxide (SiO₂) is grown on the surfacenucleation sites of the template nanosphere 600 to produce a siliconoxide-coated nanosphere 602 around the template nanosphere 600. Thetemplate nanosphere 600 is then removed (for example, by heat treatment)to produce a silicon oxide nanosphere 604.

In other embodiments, commercially available silicon oxide hollownanospheres may be obtained (block 504). For example, in someembodiments, the silicone oxide hollow nanospheres may be obtained innanopowder form from American Elements of Los Angeles, Calif., USA.

Next, the exterior surface of the silicon oxide nanospheres may befunctionalized using an alkyl silane (block 506). In some embodiments,the alkyl silane may include octyltrimethoxysilane (OTMS),octadecyltrimethoxysilane (ODTMS), or a combination thereof. In someembodiments, the functionalization of the silicon oxide nanospheres withan alkyl silane is performing according to the following procedure: 1)disperse silicon oxide nanospheres in a 200 milliliters (ml) of drytoluene via a ball-milling process; 2) transfer the dispersion to a 500ml three-necked flask with a mechanical stirrer and add an alkyl silane;3) stir the mixture at a temperature of at least 90° C. under reflux fora time period of at least 48 hours; 4) collect thesurface-functionalized silicon oxide nanospheres by centrifugation andwash with anhydrous ethanol; and 5) dry in a vacuum oven at atemperature of at least 80° C. for a time period of at least 24 hours.

FIG. 7 illustrates step 506 of the process 500 in accordance with anembodiment of the disclosure. As shown in FIG. 7, a silicon oxide hollownanosphere 700 may have an exterior surface that includes hydroxyl (OH)groups 702. An alkyl silane (for example, octadecyltrimethoxysilane 704as shown in FIG. 7) may be added to the silicon oxide hollow nanosphere700 (such as in a dispersion containing the silicon oxide hollownanosphere). The octadecyltrimethoxysilane 704 bonds to surface of thesilicon oxide hollow nanosphere 700 via interaction with the hydroxyl(OH) groups 702 to form an alkyl group 706 on the exterior surface ofthe silicon oxide hollow nanosphere 700.

As shown in FIG. 5, the surface-functionalized silicon oxide nanospheresmay be crushed using a milling process to produce the silicon oxideJanus nanosheets RPM (block 508). The silicon oxide nanospheres may becrushed using a colloid milling process. In such embodiments, thecross-sectional dimensions of the nanosheets may be tunable by adjustingthe mill spacing the between the rotators of the mill and adjusting themilling time. For example, to decrease the cross-sectional dimensions ofthe nanosheets, the spacing between the rotators may be decreased. Aftercrushing, the resulting silicon oxide Janus nanosheets RPM may have ahydrophobic side of alkyl groups (from the alkyl silanefunctionalization) and the other side having the silanol groups.

Synthesis of Silicon Oxide Janus Nano Sheets RPM for SandstoneFormations

FIG. 8 depicts a process 800 for the synthesis of a silicon oxidenanosheets RPM for a sandstone formation in accordance with anembodiment of the disclosure. As will be appreciated, the synthesisdescribed in process 800 is a one-pot synthesis. Initially, a silane oilmixture having an alkyl silane may be prepared (block 802). In someembodiments, the oil-silane mixture may include tetraethoxysilane (TEOS)and amido-propyltrimethoxysilane (APTMS). In some embodiments, the alkylsilane is octadecyltrimethoxysilane (ODTMS).

The oil-silane mixture may be emulsified with a polystyrene-polyacrylicacid multiple block copolymer such that the oil-silane mixture isdispersed in the continuous aqueous phase (block 804). The droplet sizeof the emulsion may be controlled by varying the concentration of thecopolymer. Under the acidic conditions, a sol-gel is created at theemulsion interface. The particles of the sol-gel form spheres with asilicon oxide shell having an oil core and a Janus interface (block 806)that includes external hydrophilic surface and an interior oleophilicsurface. The external hydrophilic surface includes amino groups oramines, and the internal oleophilic surface includes alkyl groups. FIG.9 depicts an example sphere formed in the emulsion according to theprocess 800. As shown in FIG. 9, the interface 900 of the emulsifieddroplet may be a Janus interface of an exterior hydrophilic surface 902having amino groups and an interior oleophilic surface 904 having alkylgroups R (for example, a C21 alkyl group produced from the example alkylsilane octadecyltrimethoxysilane (ODTMS)).

Next, the internal oil core of the spheres may be dissolved to formsilicon oxide hollow nanospheres having an exterior surface with aminogroups or amines and an interior surface with alkyl groups (block 808).For example, in some embodiments, the solvent may be hexane. As shown inFIG. 8, the silicon oxide nanospheres may be crushed using a millingprocess to produce the silicon oxide Janus nanosheets RPM for sandstoneformations (block 810). The silicon oxide nanospheres may be crushedusing a colloid milling process. In such embodiments, thecross-sectional dimensions of the nanosheets may be tunable by adjustingthe mill spacing the between the rotators of the mill and adjusting themilling time. For example, to decrease the cross-sectional dimensions ofthe nanosheets, the spacing between the rotators may be decreased. Aftercrushing, the resulting silicon oxide Janus nanosheets RPM may have ahydrophobic side of alkyl groups and a cationic side having amino groupsor amines.

Ranges may be expressed in the disclosure as from about one particularvalue, to about another particular value, or both. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value, to the other particular value, or both, along withall combinations within said range.

Further modifications and alternative embodiments of various aspects ofthe disclosure will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the embodiments described inthe disclosure. It is to be understood that the forms shown anddescribed in the disclosure are to be taken as examples of embodiments.Elements and materials may be substituted for those illustrated anddescribed in the disclosure, parts and processes may be reversed oromitted, and certain features may be utilized independently, all aswould be apparent to one skilled in the art after having the benefit ofthis description. Changes may be made in the elements described in thedisclosure without departing from the spirit and scope of the disclosureas described in the following claims. Headings used in the disclosureare for organizational purposes only and are not meant to be used tolimit the scope of the description.

What is claimed is:
 1. A silicon oxide Janus nanosheet relativelypermeability modifier (RPM), comprising: a silicon oxide nanosheethaving a first side and a second side, a functional group bonded to thefirst side, the functional group selected from the group consisting ofNH₂ and an amine; and an alkyl group linked to the second side, thealkyl group selected from the group consisting of a C8-C30 alkyl.
 2. Thesilicon oxide Janus nanosheets RPM of claim 1, wherein the alkyl groupis bonded to the second side by an oxygen atom.
 3. The silicon oxideJanus nanosheets RPM of claim 1, wherein the degree of hydrophobic alkylfunctionality of the second side is in the range of 0.01 weight (wt) %to 40 wt %.
 4. The silicon oxide Janus nanosheets RPM of claim 1,wherein the silicon oxide nanosheet has a thickness in the range of inthe range of 24 nanometers (nm) to 95 nm.
 5. A method of manufacturing asilicon oxide Janus nanosheet relatively permeability modifier (RPM),comprising: preparing a silicon oxide nanosphere, wherein preparing thesilicon oxide nanosphere comprises: preparing a template nanospherecomprising a polystyrene nanosphere; growing silicon oxide on anucleation site on a surface of the template nanosphere; and removingthe template nanosphere via heat; functionalizing the surface of thesilicon oxide nanosphere using an alkyl silane to produce asurface-functionalized silicon oxide nanosphere; and crushing thesurface-functionalized silicon oxide nanosphere to form the siliconoxide Janus nanosheets RPM, the silicon oxide Janus nanosheets RPMcomprising: a silicon oxide nanosheet having a first side and a secondside; a functional group bonded to the first side, the functional groupselected from the group consisting of COOH, COO⁻, OH, or O⁻; an alkylgroup linked to the second side, the alkyl group selected from the groupconsisting of a C8-C30 alkyl.
 6. The method of claim 5, wherein thealkyl group is bonded to the second side by an oxygen atom.
 7. Themethod of claim 5, wherein the degree of hydrophobic alkyl functionalityof the second side is in the range of 0.01 weight (wt) % to 40 wt %. 8.The method of claim 5, wherein the alkyl silane comprisesoctyltrimethoxysilane (OTMS) or octadecyltrimethoxysilane (ODTMS).
 9. Amethod of manufacturing a silicon oxide Janus nanosheet relativelypermeability modifier (RPM), comprising: preparing an oil-silane mixturecomprising an alkyl silane; adding a polystyrene-polyacrlic acid blockcopolymer to the oil-silane mixture to prepare an emulsion, the emulsioncomprising a droplet having an external hydrophilic surface and aninterior oleophilic surface; dissolving an oil core of the droplet in asolvent to form a silicon oxide hollow nanosphere; and crushing thesilicon oxide hollow nanosphere to form the silicon oxide Janusnanosheets RPM, the silicon oxide Janus nanosheets RPM comprising: asilicon oxide nanosheet having a first side and a second side; afunctional group bonded to the first side, the functional group selectedfrom the group consisting of NH₂ and an amine; and an alkyl group linkedto the second side, the alkyl group selected from the group consistingof a C8-C30 alkyl.
 10. The method of claim 9, wherein the alkyl group isbonded to the second side by an oxygen atom.
 11. The method of claim 9,wherein the alkyl silane comprises octyltrimethoxysilane (OTMS) oroctadecyltrimethoxysilane (ODTMS).
 12. The method of claim 9, whereinthe oil-silane mixture comprises tetraethoxysilane (TEOS) andamido-propyltrimethoxysilane (APTMS).
 13. The method of claim 9, whereinthe solvent comprises hexane.